According to America’s Energy Future, the national academies, United States 28% of the total energy consumption is on transportation. The transportation sector includes all modes of transportation from personal vehicles to public transportation; even the airplanes, freight trains and buses are included. In general the energy used by the airplanes is only about 9%where as for the buses and trains it is only 3%.Personal vehicles would consume a higher percentage i.e. 60%.
In, America petroleum based fuels are mostly used for transportation. The population of United States is less than 5% of the world population, but the automobile usage is of about one-third of the world’s automobile. In 2007,automobiles,cars,trucks drove for about 3 trillion miles. Over the next 20 years total number of miles driven will grow to 40% which increases the demand for the fuel.
86% of the energy used comes from gasoline and diesel fuels. The gasoline and the diesel fuels combine and emit carbon dioxide, carbon monoxide, oxides of nitrogen and unburnt hydrocarbons. As these are the dangerous gases for environment they result in green house effect.
Alternatives like bio-fuels and usage of hydrogen fuel cells makes us to reduce the usage of the petroleum. Converting coal into liquid fuel is another alternative but it also makes the environment polluted. But according to the estimation of AEF conversion of coal to liquid plants would produce 3 million barrels of gasoline by 2035; but the requirement of the coal also increases by 50% in U.S.